Studies on Plant Growth Promoting Properties of Fruit-Associated Bacteria from Elettaria cardamomum and Molecular Analysis of ACC Deaminase Gene

Abstract

Endophytic microorganisms have been reported to have diverse plant growth promoting mechanisms including phosphate solubilization, N2 fixation, production of phyto-hormones and ACC (1-aminocyclopropane-1-carboxylate) deaminase and antiphyto-pathogenic properties. Among these, ACC deaminase production is very important because of its regulatory effect on ethylene which is a stress hormone with precise role in the control of fruit development and ripening. However, distribution of these properties among various endophytic bacteria associated with fruit tissue and its genetic basis is least investigated. In the current study, 11 endophytic bacteria were isolated and identified from the fruit tissue of Elettaria cardamomum and were studied in detail for various plant growth promoting properties especially ACC deaminase activity using both culture-based and PCR-based methods. PCR-based screening identified the isolates EcB 2 (Pantoea sp.), EcB 7 (Polaromonas sp.), EcB 9 (Pseudomonas sp.), EcB 10 (Pseudomonas sp.) and EcB 11 (Ralstonia sp.) as positive for ACC deaminase. The PCR products were further subjected to sequence analysis which proved the similarity of the sequences identified in the study with ACC deaminase sequences reported from other sources. The detailed bioinformatic analysis of the sequence including homology-based modelling and molecular docking confirmed the sequences to have ACC deaminase activity. The docking of the modelled proteins was done using patch dock, and the detailed scrutiny of the protein ligand interaction revealed conservation of key amino acids like Lys51, Ser78, Tyr268 and Tyr294 which play important role in the enzyme activity. These suggest the possible regulatory effect of these isolates on fruit physiology.

Functional Diversity of Soil Bacteria from Organic Agro Ecosystem

“…Bacteria secrete siderophores to solubilize Fe from their surrounding environments by forming a complex ferric-siderophore and provide it to the plants for growth promotion (Andrews et al, 2003). Siderophore mediated suppression of phytopathogens was reported by Jasim et al, (2015). Here, a physiological response is implied by the fact that HCN production is induced by iron (Bakker and Schippers, 1987;Keel et al, 1989;Voisard et al, 1989) and that it is under the strong influence of quorum sensing (Pessi and Haas, 2000).…”

“…Studies reveal the role of ACCD in influencing the senescence of flowers and thereby increasing the shelf life (Ali et al, 2012;Jasim et al, 2015). Additionally, recent results suggest a considerable degree of horizontal ACCD gene transfer events (Nascimento et al, 2014).…”

<i>Pantoea agglomerans</i>: a mysterious bacterium of evil and good. Part IV. Beneficial effects

“…Asis and Adachi [142] isolated from the stem of sweet potato in Japan, a diazotrophic P. agglomerans strain, with a potential to increase nitrogen uptake by this important Japanese crop plant. Jasim et al [143] have recently demonstrated that the strain determined as Pantoea sp., isolated from the cardamom (Elettaria cardamomum) fruit tissue in India, showed the ability to produce ACC (1-aminocyclopropane-1carboxylate) deaminase which regulates the ethylene level in plant tissues and thereby promotes plant growth. De Almeida Lopes et al [144] have evidenced that Pantoea agglomerans and Variovorax paradoxus strains showed the highest efficiency in IAA production and phosphate solubilization among all bacterial endophytic strains isolated from soybean The tropical corn seedlings treated with P. agglomerans suspension and grown in saline soil in a greenhouse (right) showed a significant growth enhancement compared to untreated plants (left).…”

Assessment of plant growth-promoting stress-tolerant endophytes screened from Bougainvillea glabra for the growth of Triticum aestivum L. and Zea mays

“…In natural environment, plants have to combat various biotic and abiotic stresses (Balseiro-Romero et al, 2017). Abiotic stressors are classified as inanimate components associated with the environment whose effect is experienced by the living organisms of nature (Jasim et al, 2015). Nutrients, salt concentration, water availability, temperature change, and pH are the main abiotic factors that directly influence plant growth in agricultural fields (Kumar and Verma, 2018).…”

“…Several researchers (Khalifa et al, 2016;Nascimento et al, 2016) have reported lesser amounts of endophytic bacteria in plants (4 log 10 to 8 log 10 CFU/g of plant tissue) than rhizospheric bacteria (6 log 10 to 9 log 10 CFU/g of soil) in a host crop. In recent years, numerous biochemical pathways used by endophytes for enhancing plant develop-ment under various abiotic stresses were reported in scientific studies (Jasim et al, 2015). These include phytohormone production, ACC deaminase activity, HCN production, organic acid production for solubilization of minerals, and antagonistic activity (Edi-Premono et al, 1996;Carlos et al, 2016;Kumar and Verma, 2018).…”